Technical Abstract:
Peach production in the U.S. relies on standard size trees on vigorous, seedling rootstocks grown at low-densities (297 trees/ha). Production per hectare is low. Peach tree growth habits, such as pillar (P) (columnar canopy shape) and upright (U), can be planted in high-density systems with the potential for increased production per hectare. Pillar and upright, advanced breeding selections, and standard (S) ('Harrow Beauty') trees on 'Lovell' rootstock were planted at 4 densities (135 trees/ha to 1112 trees/ha) and trained to a central leader (CL) or multiple leader (ML) form. Trees were dormant pruned and trained then summer pruned (SP) in the first growing season after fall planting. One-half of the trees were SP in the second growing season after dormant pruning. Growth habit affected trunk and canopy size after two growing seasons, but training system only affected tree height. Summer pruning had no effect on trunk or canopy size. .Dormant CL training required more time than ML training for all growth habits, however, the difference was greater for U and P trees (110% more time) than for S trees (39%). Branch spreading using bands, weights, or clothespins contributed to the greater training time for CL trees. Summer pruning increased light levels in the lower canopy with the greatest effect in S and U trees. Yields in the second leaf were greater for ML trained trees than CL trees. SP reduced the yield of U trees but not S or P trees. Based on these data and observations of U and P peach trees growing on a deep, well-drained fertile site, it appears that pruning and training of U and P trees to conform to a specific form may result in excessive tree vigor. Reduced early training to allow for expression of the natural growth habit may be preferable.